1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a wireless communication terminal and a method for controlling power and using a channel by adjusting a channel bandwidth of the wireless communication terminal. More particularly, the present invention relates to a wireless communication terminal which can change a channel bandwidth for the transmission of radio signals according to environmental conditions, reduce power consumption, guarantee good communication performance by preventing interference between wireless communication terminals, and allow communications of more wireless communication terminals by assigning part of the channel bandwidth to newly-entering wireless communication terminals when every channel is in use, and a method of power control and channel use incorporating such adjustment of channel bandwidth.
2. Description of the Related Art
Bluetooth, which is recently attracting attention in the wireless communication, is a short-distance radio communication standard. Bluetooth enables bidirectional communications among digital devices in real time by wirelessly connecting a mobile phone, a computer, and a personal digital assistant (PDA) within 10˜100 m with a phone, a computer, and home appliances in home or office. Frequency band of Bluetooth ranges 2.402˜2.480 GHz which is the Industrial, Scientific, and Medical (ISM) bands of 2.4 GHz.
If two wireless terminals communicating with each other, through Bluetooth are referred to as a transmitter terminal and a receiver terminal, respectively, the pair of the transmitter terminal and the receiver terminal can be a mobile terminal and a wireless headset, a computer and a wireless headset, a computer and a peripheral, and the like.
To prevent interference between the receiver terminals at a short distance, the Bluetooth utilizes a frequency hopping which is a kind of spread spectrum method. The frequency hopping, which changes the frequencies at random, defines 79 frequency bands by dividing the bandwidth by 1 MHz in the Bluetooth band of 2.402˜2.480 GHz and converts frequency bands to transmit signals. The frequency band conversion is carried out 1600 times per one second.
Mostly, one receiver terminal is connected to one transmitter terminal for radio communications. At the initial communication, the transmitter terminal matches the channel between the transmitter terminal and the receiver terminal by sending radio signals to the receiver terminal in a preset channel. Herein, the channel is a kind of codes formed through the frequency hopping, and the channel can be set based on in which order 79 frequency bands, which are divided for the frequency hopping, are converted. For instance, if the divided frequency bands are referred to as 1st through 79th bands, the channel 1 can sequentially hop the 1st through 79th bands and the channel 2 can hop the 5th band, the 29th band, the 17th band, the 3rd band, . . . in that order.
Ultra-wideband wireless communication is under development using the ultra-wideband frequency band of 3.1˜5.1 GHz. The ultra-wideband wireless communication transmits and receives communication signals primarily using on-off keying (OOK) modulation which transmits and receives digital signals as ON and OFF. To prevent the interference with other transmitter terminals, the OOK modulation generates a channel by dividing the frequency band of 3.1˜5.1 GHz to a plurality of bands. The transmitter terminal and the receiver terminal communicate with each other using the selected channel of the divided bands.
In the ultra-wideband chaotic communication system using the OOK modulation, since the frequency power density is defined according to the standard specification, the wireless power intensity is determined by the bandwidth of the used channel. Accordingly, the power consumption of the battery is determined. The wider channel frequency bandwidth, the more power consumption of the battery. Although the channel bandwidth is determined to optimize the channel communication state, the communication state may be good without using the whole channel bands depending on the channel environment. However, since the channel bandwidth is not technically adjustable up to now, the channel bandwidth is always the same. Hence, disadvantageously, the power is wasted in the good channel environment.
The power consumption can be reduced by narrowing the channel bandwidth in a good channel environment.
When the pairs of the transmitter terminal and the receiver terminal equal the number of the channels which reside within a certain wireless communication range, that is, when all channels are occupied, a new transmitter terminal 1 and a new receiver terminal 1 may enter the wireless communication range. In this case, communication interference occurs between the new transmitter terminal 1 and the new receiver terminal 1, and between the transmitter terminals using the same channel, and the radio communications fail to both sides.
This disadvantage results from the fixed channel bandwidth and the fixed number of channels in the OOK modulation. Therefore, to overcome it, a new channel is generated by adjusting the channel bandwidth.